The ethical problem of thinking about our responsibility to future generations is compounded by the fact that it is we who create those generations, and we can determine, in principle, how many lives there shall be. Questions raised include whether more lives are preferable to fewer lives, if all are worth living, and how to balance the resulting competition between quantity and quality. ‘Total’ utilitarianism sums the imagined utility of each life; ‘average’ utilitarianism looks at the average utility. Each is open to problems. Other questions concerning non-existent persons arise if we ask what kind of duty is violated if we choose to have a child with a predictable disability, now, rather than waiting and generating a normal child a little later. No person seems to be harmed by the former decision (for the disabled child does not exist on the other alternative), yet it seems callous and wrong. See also Parfit.